I. buff up phrasal verb informal ( see also ↑ buff )
to exercise in order to make your muscles bigger:
Smith buffed up for his role as Muhammad Ali.
II. buff 2 BrE AmE ( also buff up ) verb [transitive]
[ Date: 1800-1900 ; Origin: ⇨ ↑ buff 1 ; because leather was used for polishing ( ⇨ ↑ buff 1 (2) ) ]
to polish something with a cloth:
Sandra was buffing her nails.
buff up phrasal verb informal
to exercise in order to make your muscles bigger:
Smith buffed up for his role as Muhammad Ali.